The great mental models volume 1 by Shane Parrish and Rhiannon Beaubien

I enjoyed reading this book. It is well written and goes down easy. Each chapter starts with a list of people who are linked to the topic introduced in the chapter, which I thought was a very nice addition to the book. None of the topics covered in this book were new to me, I have read about these concepts before, but it was nice to read about them again. For anyone interested in mental models (and indirectly systems thinking), this is a nice introduction.

Topics covered in this book are:

  • The map is not the territory
  • Circle of competence
  • First principles thinking
  • Thought experiment
  • Second-order thinking
  • Probalistic thinking
  • Inversion
  • Occam’s razor
  • Hanlon’s razor


Education doesn’t prepare you for the real world. At least, it didn’t prepare me. (Location 53)

Acquiring Wisdom

When understanding is separated from reality, we lose our powers. Understanding must constantly be tested against reality and updated accordingly. (Location 155)

If you don’t test your ideas against the real world — keep contact with the earth — how can you be sure you understand? (Location 159)

Our failures to update from interacting with reality spring primarily from three things: not having the right perspective or vantage point, ego - induced denial, and distance from the consequences of our decisions. (Location 166)

The first flaw is perspective. We have a hard time seeing any system that we are in. (Location 169)

The second flaw is ego. Many of us tend to have too much invested in our opinions of ourselves to see the world’s feedback — the feedback we need to update our beliefs about reality. (Location 179)

The third flaw is distance. The further we are from the results of our decisions, the easier it is to keep our current views rather than update them. (Location 184)

We also tend to undervalue the elementary ideas and overvalue the complicated ones. (Location 199)

We have a tendency to think that how the world is, is how it always was. And so we get caught up validating our assumptions from what we find in the here and now. (Location 293)

The Map is not the Territory

If a map were to represent the territory with perfect fidelity , it would no longer be a reduction and thus would no longer be useful to us. (Location 394)

A map can also be a snapshot of a point in time, representing something that no longer exists. (Location 395)

Supporting Idea: Falsifiability

Too frequently, these postulated laws become immune to falsifying evidence — any new evidence is interpreted through the lens of the theory. (Location 741)

First Principles Thinking

First principles are the boundaries that we have to work within in any given situation — so when it comes to thermodynamics an appliance maker might have different first principles than a physicist. (Location 784)

Supporting Idea: Necessity and Sufficiency

We often make the mistake of assuming that having some necessary conditions in place means that we have all of the sufficient conditions in place for our desired event or effect to occur. (Location 1034)

Second-Order Thinking

«Stupidity is the same as evil if you judge by the results.» (Location 1077)

Probabilistic Thinking

Probabilistic thinking is essentially trying to estimate, using some tools of math and logic, the likelihood of any specific outcome coming to pass. (Location 1197)

Conditional probability is similar to Bayesian thinking in practice, but comes at it from a different angle. When you use historical events to predict the future, you have to be mindful of the conditions that surrounded that event. (Location 1242)


Instead of thinking through the achievement of a positive outcome, we could ask ourselves how we might achieve a terrible outcome, and let that guide our decision-making. (Location 1501)

Hanlon’s Razor

Hanlon’s Razor states that we should not attribute to malice that which is more easily explained by stupidity. (Location 1712)

Always assuming malice puts you at the center of everyone else’s world. This is an incredibly self-centered approach to life. (Location 1744)

Version of the book

Parrish, Shane; Beaubien, Rhiannon. The Great Mental Models Volume 1: General Thinking Concepts. Latticework Publishing Inc.. Kindle Edition.